In an imaging device, a shutter speed represents a period of time a shutter stays open when the camera takes a photo. The shutter speed may decide, together with a size of a lens aperture (also known as an F-number), an amount of light reaching a film or a sensor, also known as exposure. The faster the shutter speed, the shorter an exposure time, and the less the exposure. However in this case, a moving object may leave a clearer image on the film. The slower the shutter speed, the longer the exposure time, and the more the exposure. However in this case, the image of the moving object on the film will appear fuzzy. In general, imaging with a shutter speed of 1/30 second or less may be called imaging with a slow shutter speed. Using imaging with a slow shutter speed, a photo with a special effect or an artistic effect may be obtained.
In related art, during imaging with a slow shutter speed, an imaging device may collect image data at regular intervals, and continuously generate images using the image data, thereby displaying an exposure effect in real time. However, in related art image data are collected continuously at fixed intervals, instead of at intervals variable as needed. Different imaging devices may process data at different speeds. An imaging device may process data at different speeds under different circumstances. When an overly large interval is set, the exposure effect will not be displayed in real time, impacting user experience. When an overly short interval is set, image data collected in time may go beyond computing capacity of an imaging device, leading to data loss.